Confidence in temperature

Using column temp, we can compute the sample mean

temp = 19:74, sample size = 150 and the sample standard deviation stemp = 6:035.

(a) Construct a 91% confidence interval for the population mean of

temp.

(b) If we want ensure the error margin of the 91% confidence interval to be less than 0.5, what sample size should we take (assuming that the sample standard deviation is a good estimate of the population standard deviation)?

is the error margin of the 91% confidence interval different to the error margin of x-bar? (s\sqrt{n}), how would you calc the approx sample size?

2. Construct a 95% confidence interval for the proportion of forest fires that occur when the temperature is greater than 25 degrees celsius.

I found the values in the data set >25 degrees which made n=21, x-bar=28.533 and s=2.467, then I just did the normal confidence interval formula to work it out. Did I go about that the right way?;)

Cheers,

Jay

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